This group has recently completed enrollment on the PRospective, Observational, Multi-center Massive Transfusion sTudy (PROMMTT) to evaluate the process, the decision-making, and outcomes associated with MT. This trial is supported by a ten million dollar grant from the U.S. Department of Defense for the Center for Translational Injury Research (CeTIR) and it investigators to conduct a multi-site observational study of severely injured trauma patients who require blood transfusions. Through our efforts, we hope to determine the best method of identifying patients who will benefit from receiving different ratios of red blood cells to plasma to platelets. This study was also designed to evaluate existing MT protocols at ten leading trauma centers and to identify which protocols are associated with better survival. Results of this study will be used to develop a future randomized clinical trial that will test these protocols.